1. Field of the Invention
The present invention relates to an optical communication module and an optical communication module product.
2. Related Background Art
An optical communication module comprises a semiconductor laser; an optical fiber for receiving light from the semiconductor laser; a light-receiving device for monitoring light from the semiconductor laser; and a package for containing the light-receiving device, semiconductor laser, and optical fiber therein.
FIG. 16 is a perspective view showing the configuration of an optical transmission module 90 for technical studies. The optical transmission module 90 is used as a light source in optical communications. The inventors have studied a configuration of an optical transmission module in which a coaxial connector 91b of SMA type, GPO type, or the like is provided on a side face of a butterfly type package 92 in order to transmit positive-phase and complementary negative-phase signals, both including a high-frequency component of 2.5 GHz or higher, from the outside to inside of the package, thereby attaining impedance matching for the positive- and negative-phase signals. As shown in FIG. 16, such an optical transmission module has the single coaxial connector 91b on a package side orthogonal to an optical fiber supporting face 93 supporting an optical fiber 94. Due to restrictions on dimensions of the coaxial connector 91b itself, the coaxial connector 91b can not be provided on a package side opposed to the optical fiber supporting face 93. Further, mounting the optical transmission module with a pair of coaxial connectors makes it necessary to increase the size of the optical transmission module.
FIG. 17 is a view showing a configuration of the optical transmission module 90 mounting a circuit board 95 thereon. The circuit board 95 is mainly constituted by the optical transmission module 90 comprising the coaxial connector 91b, and an electric circuit unit 96 including an electric device 98 and a coaxial connector 91a. The electric circuit unit 96 controls the optical transmission module 90. The optical transmission module 90 is connected via a coaxial cable 97 to the electric circuit unit 96 of the circuit board 95 in order to feed positive-phase and negative-phase signals both including a high-frequency component of 2.5 GHz or higher into the optical transmission module 90. The coaxial cable 97 connects the coaxial connectors 91a and 91b to each other. In optical transmission module 90, the optical fiber supporting face 93 is provided with the optical fiber 94 through which light emitted from the optical transmission module 90 propagates. In the optical transmission module 90, the optical fiber 94 is positioned at the optical fiber supporting face 93, and it is necessary that the optical fiber supporting face 93 be provided so as to face one side 95a of the circuit board 95. For obtaining flexibility in designing the circuit board 95, it is necessary that the electric circuit unit 96 be provided to face another side 95b of the circuit board 95 opposed to the side 95a. The coaxial cable 97 connects the coaxial connector 91a provided in the electric circuit unit 96 and the coaxial connector 91b provided in the optical transmission module 90 to each other, and is disposed in a mounting surface of the circuit board 95 so as to extend along a smooth curve to eliminate the deterioration of high-frequency signals propagating through the coaxial cable 97. For this connection, the coaxial cable 97 is required to have a length of at least 4 to 5 cm. The inventors have found that the coaxial cable 97 further necessitates the mounting portion therefor and that this mounting portion limits the reduction of the circuit board 95 in size.
The inventors think that dimensions of the coaxial connector 91b impose limitations on the reduction of height in the optical transmission module 90. The inventors also think that it is necessary to reduce the size of the optical transmission module 90, the package of the optical transmission module 90 in particular, in response to meeting recent demands for small-sized optical transmission apparatuses.
The inventors also think that there are demands for optical transmission modules capable of high-speed operations. Recently, optical transmission modules are required to operate to receive a driving signal including a frequency component of 10 GHz or higher, for example.
It is an object of the present invention to provide an optical transmission module operable to receive a positive-phase signal and a complementary negative-phase signal both including a high-frequency component of 10 GHz or higher, and to provide an optical communication module product including a circuit board implemented with this optical transmission module.
One aspect of the present invention relates to an optical transmission module. The optical transmission module comprises a semiconductor laser element, a semiconductor circuit element, and a package. The semiconductor laser element emits light. The semiconductor circuit element drives the semiconductor laser element, receives a positive-phase signal and a complementary signal both including a high-frequency component, converts thus received signals into a single-ended signal, and provides thus obtained single-ended signal to the semiconductor laser element. The package contains the semiconductor laser element and semiconductor circuit element therein and comprises an optical fiber supporting face supporting an optical fiber thereon for transmitting light emitted from the semiconductor laser element. The optical transmission module comprises a lead pin for receiving the positive-phase signal and a lead pin for receiving the negative-phase signal on a back face, opposed to the optical fiber supporting face, of the package. These lead pins are provided so as to pass through the back face.
Another aspect of the present invention relates to an optical communication module. The optical communication module comprises a housing, a semiconductor light-emitting element, and a semiconductor element. The housing has first to fourth walls. The first wall is provided with an optical fiber accommodating portion extending in a predetermined axial direction. Each of the second and third walls extends in the predetermined axial direction and has a plurality of lead terminals thereon. The fourth wall is provided to be opposes to the first wall, and has a plurality of lead terminals. The semiconductor element has a first group of input terminals, an output terminal, and a second group of a plurality of terminals. The input terminals in the first group receive signals for differential operation to drive the semiconductor light-emitting element. The output terminal provides a driving signal from the signals for differential operation. The terminals in the second group are provided to be separated from the input and output terminals. In the semiconductor element, the terminals in the second group are connected to the lead terminals on the second and third walls. The semiconductor light-emitting element is connected to the semiconductor device.
Still another aspect of the present invention relates to an optical communication module product. The optical communication module product comprises an optical communication module, an electronic component, and a substrate. The electronic component generates signals for differential operation to drive the semiconductor light-emitting element. The substrate comprises a wiring member and a mounting member. The wiring member has a wiring layer for connecting the electronic component to the first and second lead terminals of the optical communication module. The mounting member mounts the optical communication module, electronic component, and wiring member. The wiring member has an opening capable of receiving the optical communication module therein. The opening has a side provided to face the fourth wall.
The above-mentioned object and other objects, features, and advantages of the present invention will more easily be seen from the following detailed description of preferred embodiments of the present invention set forth with reference to the accompanying drawings.